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Abstract:

Aspects of a method and system for channel estimation for interference
suppression are provided. In this regard, one or more circuits and/or
processors of a mobile communication device may generate and/or receive a
first set of channel estimates and a second set of channel estimates. The
one or more circuits and/or processors may modify the second set of
channel estimates based on a comparison of a measure of correlation
between the first set of channel estimates and the second set of channel
estimates with a threshold. The first set of channel estimates and/or the
modified second set of channel estimates may be utilized for cancelling
interference in received signals. The first set of channel estimates may
be associated with a first transmit antenna of a base transceiver station
and the second set of channel estimates may be associated with a second
transmit antenna of the base transceiver station.

Claims:

1. A signal processing system, comprising: a first receiver configured to
generate a first set of channel estimates; a second receiver configured
to generate a second set of channel estimates; and an interference
cancellation module coupled to the first and second receivers and
configured to: determine a value of a correlation between the first set
of channel estimates and the second set of channel estimates; modify the
second set of channel estimates based on the determined value of the
correlation; and cancel interference in a received signal utilizing the
first set of channel estimates and the modified second set of estimates.

2. The signal processing system of claim 1, wherein the interference
cancellation module is configured to determine a threshold of the value
of the correlation.

3. The signal processing system of claim 2, wherein the interference
cancellation module is configured to modify the second set of channel
estimates by setting each estimate to zero when the value of the
correlation is above the threshold.

4. The signal processing system of claim 2, wherein the interference
cancellation module is configured to modify the second set of channel
estimates by rotating the second set of channel estimates such that it is
orthogonal to the first set of channel estimates when the value of the
correlation is below the threshold.

5. The signal processing system of claim 2, wherein the threshold is
determined dynamically.

6. The signal processing system of claim 1, wherein the first set of
channel estimates are associated with one or more RF channels between, a
first base transceiver station (BTS) and a mobile communication device.

7. The signal processing system of claim 6, further comprising a
normalization module configured to normalize the first set of channel
estimates with respect to total power received from the first BTS.

8. The signal processing system of claim 1, wherein the second set of
channel estimates are associated with one or more RF channels between a
second base transceiver station (BTS) and a mobile communication device.

9. The signal processing system of claim 8, further comprising a
normalization module configured to normalize the second set of channel
estimates with respect to total power received from the second BTS.

10. The signal processing system of claim 1, wherein each channel
estimate in the first and second sets of channel estimates indicates a
complex channel gain between a transmit antenna and one or more receive
antennas.

11. A method of processing signals using a communications device,
comprising: determining a value of a correlation between a first set of
channel estimates and a second set of channel estimates; modifying the
second set of channel estimates based on the determined value of the
correlation; and canceling interference in a received signal utilizing
the first set of channel estimates and the modified second set of
estimates.

12. The method of claim 11, further comprising determining a threshold of
the value of the correlation.

13. The method of claim 12, wherein the second set of channel estimates
is modified by setting each estimate to zero when the value of the
correlation is above the threshold.

14. The method of claim 12, wherein the second set of channel estimates
is modified by rotating the second set of channel estimates such that it
is orthogonal to the first set of channel estimates when the value of the
correlation is below the threshold.

15. The method of claim 12, wherein the threshold is determined
dynamically.

16. The method of claim 11, wherein the first set of channel estimates
are associated with one or more RF channels between a first base
transceiver station (BTS) and a mobile communication device.

17. The method of claim 16, further comprising normalizing the first set
of channel estimates with respect to total power received from the first
BTS.

18. The method of claim 11, wherein the second set of channel estimates
are associated with one or more RF channels between a second base
transceiver station (BTS) and a mobile communication device.

19. The signal processing system of claim 18, normalizing the second set
of channel estimates with respect to total power received from the second
BTS.

20. A non-transitory computer readable medium containing computer
instructions that, when executed by one or more processors, cause the one
or more processors to perform actions comprising: determining a value of
a correlation between a first set of channel estimates and a second set
of channel estimates; modifying the second set of channel estimates based
on the determined value of the correlation; and canceling interference in
a received signal utilizing the first set of channel estimates and the
modified second set of estimates.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent application Ser.
No. 12/615,237, filed on Nov. 9, 2009, which is incorporated herein by
reference in its entirety. This application also makes reference to:

[0019] Each of the above referenced applications is hereby incorporated
herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0020] 1. Field of the Invention

[0021] Certain embodiments of the invention relate to signal processing.
More specifically, certain embodiments of the invention relate to a
method and system for channel estimation for interference suppression.

[0022] 2. Related Art

[0023] Wideband code division multiple access (WCDMA) is a third
generation (3G) cellular technology that enables the concurrent
transmission of a plurality of distinct digital signals via a common RF
channel. WCDMA supports a range of communications services that include
voice, high speed data and video communications. One such high speed data
communications service, which is based on WCDMA technology, is the high
speed downlink packet access (HSDPA) service.

[0024] WCDMA is a spread spectrum technology in which each digital signal
is coded or "spread" across the RF channel bandwidth using a spreading
code. Each of the bits in the coded digital signal is referred to as a
"chip", A given base transceiver station (BTS), which concurrently
transmits a plurality of distinct digital signals, may encode each of a
plurality of distinct digital signals by utilizing a different spreading
code for each distinct digital signal. At a typical BTS, each of these
spreading codes is referred to as a Walsh code. The Walsh coded digital
signal may in turn be scrambled by utilizing a pseudo normal (PN) bit
sequence to generate chips. An example of a PN bit sequence is a Gold
code. Each of a plurality of BTS within an RF coverage area may utilize a
distinct PN bit sequence. Consequently, Walsh codes may be utilized to
distinguish distinct digital signals concurrently transmitted from a
given BTS via a common RF channel while PN bit sequences may be utilized
to distinguish digital signals transmitted by distinct STSs. The
utilization of Walsh codes and PN sequences may increase RF frequency
spectrum utilization by allowing a larger number of wireless
communications to occur concurrently within a given RF frequency
spectrum. Accordingly, a greater number of users may utilize mobile
communication devices, such as mobile telephones, Smart phones and/or
wireless computing devices, to communicate concurrently via wireless
communication networks.

[0025] A user utilizing a mobile communication device, MU_1, may be
engaged in a communication session with a user utilizing a mobile
communication device MU_2 via a base transceiver station, BTS_A within
wireless communication network. For example, the mobile communication
device MU_1 may transmit a digital signal to the BTS_A, which the base
transceiver station BTS_A may then transmit to the mobile communication
device MU_2. The base transceiver station BTS_A may encode signals
received from the mobile communication device MU_1 and transmitted to the
mobile communication device MU_2 by utilizing a Walsh code, W_12, and a
PN sequence, PN_A. The mobile communication device MU_2 may receive
signals transmitted concurrently by a plurality of base transceiver
stations (BTSs) in addition to the base transceiver station BTS_A within
a given RF coverage area. The mobile communication device MU_2 may
process the received signals by utilizing a descrambling code that is
based on the PN sequence PN_A and a despreading code that is based on the
Walsh code W_12. In doing so, the mobile communication device MU_2 may
detect a highest relative signal energy level for signals received from
base transceiver station BTS_A, which comprise a digital signal
corresponding to mobile communication device MU_1.

[0026] However, the mobile communication device MU_2 may also detect
signal energy from the digital signals, which correspond to signals from
mobile communication devices other than the mobile communication device
MU_1. The other signal energy levels from each of these other mobile
communication devices may be approximated by Gaussian white noise, but
the aggregate noise signal energy level among the other mobile
communication device may increase in proportion to the number of other
mobile communication devices whose signals are received at the mobile
communication device MU_2. This aggregate noise signal energy level may
be referred to as multiple access interference (MAI). The MAI may result
from signals transmitted by the base transceiver station BTS_A, which
originate from signal received at the base transceiver station BTS_A from
mobile communication devices other than mobile communication device MU_1.
The MAI may also result from signals transmitted by the base transceiver
stations BTSs other than the base transceiver station BTS_A. The MAI and
other sources of noise signal energy may interfere with the ability of
MU_2 to successfully decode signals received from MU_1.

[0027] An additional source of noise signal energy may result from
multipath interference. The digital signal energy corresponding to the
mobile communication device MU_2, which is transmitted by the base
transceiver station BTS_A may disperse in a wavefront referred to as a
multipath. Each of the components of the multipath may be referred to as
a multipath signal. Each of the multipath signals may experience a
different signal propagation path from the base transceiver station BTS_A
to the mobile communication device MU_2. Accordingly, different multipath
signals may arrive at different time instants at the mobile communication
device MU_2. The time duration, which begins at the time instant that the
first multipath signal arrives at the mobile communication device MU_2
and ends at the time instant that the last multipath signal arrives at
the mobile communication device MU_2 is referred to as a delay spread.
The motile communication device MU_2 may utilize a rake receiver that
allows the mobile communication device MU_2 to receive signal energy from
a plurality of multipath signals received within a receive window time
duration. The receive window time duration may comprise at least a
portion of the delay spread time duration. Multipath signals, which are
not received within the receive window time duration may also contribute
to noise signal energy.

[0028] Further limitations and disadvantages of conventional and
traditional approaches will become apparent to one of skill in the art,
through comparison of such systems with some aspects of the present
invention as set forth in the remainder of the present application with
reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

[0029] A method and system for channel estimation processing for
interference suppression, substantially as illustrated by and/or
described in connection with at least one of the figures, as set forth
more completely in the claims.

[0030] These and other advantages, aspects and novel features of the
present invention, as well as details of an illustrated embodiment
thereof, will be more fully understood from the following description and
drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0031] FIG. 1A is a diagram illustrating an exemplary wireless
communication system, which is operable to provide interference
suppression in WCDMA, in accordance with an embodiment.

[0032] FIG. 1B is a diagram illustrating an exemplary wireless
communication system, which is operable to utilize transmit diversity and
provide interference suppression in WCDMA, in accordance with an
embodiment.

[0033]FIG. 2 is a diagram of an exemplary communication device, which is
operable to provide interference suppression for WCDMA, in accordance
with an embodiment of the invention.

[0034] FIG. 3 is a diagram of an exemplary WCDMA receiver with
interference suppression, in accordance with an embodiment of the
invention.

[0035] FIG. 4 is a module diagram illustrating an exemplary interference
cancellation module, in accordance with an embodiment of the invention.

[0036]FIG. 5 is a diagram illustrating generation of normalized channel
estimates, in accordance with an embodiment of the invention.

[0037]FIG. 6A is a is a diagram that illustrates exemplary
orthogonalization of channel estimates received from a transmit diversity
antenna, in accordance with an embodiment of the invention.

[0038] FIGS. 6B and 6C are diagrams that illustrate exemplary
implementation of an orthogonalization module, in accordance with an
embodiment of the invention.

[0039] FIG. 7 is a diagram that illustrates an exemplary implementation of
a normalization module, in accordance with an embodiment of the
invention.

[0040] FIG. 8 is a flowchart illustrating exemplary steps for interference
cancellation in a communication system that utilizes transmit diversity,
in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0041] Certain embodiments of the invention may be found in a method and
system for channel estimation for interference suppression. In various
embodiments of the invention, one or more circuits and/or processors of a
mobile communication device may generate and/or receive a first set of
channel estimates and a second set of channel estimates. The first set of
channel estimates may be associated with a plurality of RF channels
between a first transmit antenna of a base transceiver station and one or
more receive antennas of the mobile communication device. The base
transceiver station may be a non-listened base transceiver station. The
second set of channel estimates may be associated with a plurality of RF
channels between a second transmit antenna of the base transceiver
station and one or more receive antennas of the mobile communication
device. The one or more circuits and/or processors may modify the second
set of channel estimates based on a comparison of a measure of
correlation between the first set of channel estimates and the second set
of channel estimates with a threshold. The threshold may be dynamically
or statically determined. The first set of channel estimates and/or the
modified second set of channel estimates may be utilized for processing
received signals. In instances that the measure of correlation is below
the threshold, the second set of channel estimates may be modified such
that the modified second set of channel estimates is orthogonal to the
first set of channel estimates. In instances that the measure of
correlation is above the threshold, the second set of channel estimates
may be modified by setting each of the channel estimates in the second
set to zero.

[0042] The first set of channel estimates may be normalized with respect
to total power received over all of the plurality of RF channels between
the first transmit antenna and the one or more receive antennas. The
second set of channel estimates may be normalized with respect to total
power received over all of the plurality of RF channels between the
second transmit antenna and the one or more receive antennas. The second
set of channel estimates may be disregarded in instances that the measure
of correlation is above a threshold. Each channel estimate in the first
set of channel estimates may indicate a vector of complex channel gains
between the first transmit antenna and one of the one or more receive
antennas. Each channel estimate in the second set of channel estimates
may indicates a complex channel gain between the second transmit antenna
and one of the one or more receive antennas. Interference may be
suppressed in the received signals based on the first set of channel
estimates and/or the modified second set of channel estimates.

[0043] FIG. 1A is an illustration of an exemplary wireless communication
system, in accordance with an embodiment. Referring to FIG. 1A, there is
shown a cell 100 and a BTS C 106. The cell 100 comprises BTS A 102, BTS B
104, mobile communication device MU_1 112 and mobile communication device
MU_2 114. The BTS 106 may be located outside of the cell 100.

[0044] The mobile communication devices MU_1 112 and MU_2 114 may be
engaged in a communication via the BTS A 102. The mobile communication
device MU_1 112 may transmit signals to the BTS A 102 via an uplink RF
channel 122. In response, the BTS A 102 may transmit signals to the
mobile communication device MU_2 114 via a downlink RF channel 124.
Signals transmitted by the BTS A 102 may communicate chips that are
generated utilizing a scrambling code PN_A. The signals transmitted via
RF channel 124 may be spread utilizing a spreading code WC_12. The
spreading code WC_12 may comprise an orthogonal variable spreading factor
(OVSF) code, for example a Walsh code, which enables the mobile
communication device MU_2 114 to distinguish signals transmitted by the
BTS A 102 via the downlink RF channel 124 from signals transmitted
concurrently by the BTS A 102 via other downlink RF channels, for example
downlink RF channel 126. The BTS A 102 may utilize one or more OVSF
codes, WC_other, when spreading data transmitted via downlink RE channel
126. The one or more OVSF codes, WC_other, may be distinct from the OVSF
code WC_12.

[0045] The mobile communication device MU_2 114 may receive MAI signals
from RF channel 126, RF channel 128 and/or RF channel 130. As stated
above, the signals received via RF channel 126 may be transmitted by the
BTS A 102. The signals received via RF channel 128 may be transmitted by
the BTS B 104. The signals transmitted by the BTS 104 may be scrambled
based on a scrambling code PN_B. The signals received via RF channel 130
may be transmitted by the BTS C 106. The signals transmitted by the BTS C
106 may be scrambled based on a scrambling code PN_C.

[0046] The mobile communication device MU_2 114 may be operable to perform
a soft handoff from the current serving BTS A 102 to any of a plurality
of BTSs located within the cell 100, for example, the BTS B 104.
Accordingly, the mobile communication device MU_2 114 may be operable to
process received signals based on scrambling code PN_A and/or scrambling
code PN_B. In this regard, the mobile communication device MU_2 114 may
send data to the BTS A 102 and/or the BTS B 104, and data destined for
mobile communication device MU_2 114 may be received via the BTS A 102
and/or the BTS B 104. Thus, the BTS A 102 and the BTS B 104 may be
referred to as "listened" BTSs. Conversely, the mobile communication
device MU_2 114 may not be operable to perform a soft handoff from the
current serving BTS A 102 to a BTS that is outside of the cell 100--the
BTS C 106, for example. In this regard, the mobile communication device
MU_2 114 may not transmit data to the BTS C 106 or receive data destined
for the mobile communication device MU_2 114 from the BTS C 106.
Accordingly, the BTS A 102 and the BTS B 104 may be referred to as
"non-listened" BTSs.

[0047] While the desired signal at the mobile communication device MU_2
114 may be received via RF channel 124, the mobile communication device
MU_2 114 may also receive signal energy via the RF channel 126, the RF
channel 128 and/or the RF channel 130. The received signal energies from
the RF channels 126, 128 and/or 130 may result in MAI, which may
interfere with the ability of the mobile communication device MU_2 114 to
receive desired signals via RF channel 124. Accordingly, in various
aspects of the invention, the mobile communication device MU_2 114 is
operable to suppress interference resulting from undesired signals
transmitted by listened BTSs. Additionally, even though the BTS is not a
listened BTS, information transmitted on the RF channel 130--data
transmitted to mobile communication devices other than mobile
communication device MU_2 114--may nevertheless interfere with the
desired signals on the RF channel 124. Accordingly, in, various aspects
of the invention, the mobile communication device MU_2 114 is operable to
suppress interference from the non-listened BTS 106, or non-listened
BTSs.

[0048] In various embodiments of the invention, the mobile communication
device MU_2 may comprise suitable logic, circuitry and/or code that are
operable to receive signal energy via the RF channels 124, 126, 128
and/or 130, and suppress interference signal energy received via the RF
channels 126, 128 and/or 130. The mobile communication device MU_2 may
utilize an iterative method for interference cancellation. The iterative
method may comprise a weighting iteration, one or more weighting and
addback iterations, and an addback iteration. For the mobile
communication devices 112 and 114 to process multipath information, each
of the channels 124, 126, 128, and 130 of FIG. 1A may represent multiple
paths, where those multiple paths are separated by a time delay.

[0049] FIG. 1B is a diagram illustrating an exemplary wireless
communication system, which is operable to utilize transmit diversity and
provide interference suppression in WCDMA, in accordance with an
embodiment. In FIG. 1B, the BTS 102 is operable transmit a datastream via
antennas 152A and 152D. The datastream may be scrambled utilizing
scrambling code PN_A, and spread utilizing spreading code WC_12, before
being transmitted via antenna 152A onto RF channel 124. Additionally, the
datastream may be scrambled utilizing scrambling code PN_D, and spread
utilizing spreading code WC_12, before being transmitted via antenna 152D
and RF channel 156. The mobile communication device 114 may be operable
to receive and process both channels 156 and 124 such that signal
reception is improved over the case in which only a single channel 124 is
present. Accordingly, aspects of the invention may enable estimating
energy present on the channels 156 and 124 and utilizing the channel
estimates to cancel or suppress interference received on the channels 156
and 124. For the mobile communication devices 112 and 114 operable to
process multipath information, each of the channels 124, 128, 130 and 156
of FIG. 1B may represent multiple paths, where those multiple paths are
separated by a time delay

[0050]FIG. 2 is a diagram of an exemplary communication device, which may
utilize interference suppression for WCDMA, in accordance with an
embodiment of the invention. Referring to FIG. 2, there is shown a
transceiver system 200, a receiving antenna 222 and a transmitting
antenna 232. The transceiver system 200 may comprise at least a receiver
202, a transmitter 204, a processor 206, an interference cancellation
module 210 and a memory 208. Although a separate receiver 202 and
transmitter 204 are illustrated by FIG. 2, the invention is not limited.
In this regard, the transmit function and receive function may be
integrated into a single transceiver module. The transceiver system 200
may also comprise a plurality of transmitting antennas and/or a plurality
of receiving antennas, for example to support diversity transmission
and/or diversity reception. Various embodiments of the invention may
comprise a single antenna, which is coupled to the transmitter 204 and
receiver 202 via a transmit and receive (T/R) switch. The T/R switch may
selectively couple the single antenna to the receiver 202 or to the
transmitter 204 under the control of the processor 206, for example.

[0051] The receiver 202 may comprise suitable logic, circuitry, interfaces
and/or code that may be operable to perform receive functions that may
comprise PHY layer function for the reception or signals. These PHY layer
functions may comprise, but are not limited to, the amplification of
received RF signals, generation of frequency carrier signals
corresponding to selected RF channels, for example uplink or downlink
channels, the down-conversion of the amplified RF signals by the
generated frequency carrier signals, demodulation of data contained in
data symbols based on application of a selected demodulation type, and
detection of data contained in the demodulated signals. The RF signals
may be received via the receiving antenna 222. The receiver 202 may be
operable to process the received RF signals to generate baseband signals.
A chip-level baseband signal may comprise a plurality of chips. The
chip-level baseband signal may be descrambled based on a PN sequence and
despread based on an OVSF code, for example a Walsh code, to generate a
symbol-level baseband signal. The symbol-level baseband signal may
comprise a plurality of data symbols. The receiver 202 may comprise a
rake receiver, which in turn comprises a plurality of rake fingers to
process a corresponding plurality of received multipath signals.

[0052] The transmitter 204 may comprise suitable logic, circuitry,
interfaces and/or code that may be operable to perform transmit functions
that may comprise PITY layer function for the transmission or signals.
These PHY layer functions may comprise, but are not limited to modulation
of received data to generate data symbols based on application of a
selected modulator type, generation of frequency, carrier signals
corresponding to selected RF channels, for example uplink or downlink
channels, the up-conversion of the data symbols by the generated
frequency carrier signals, and the generation and amplification of RF
signals. The RE signals may be transmitted via the transmitting antenna
232.

[0053] The memory 208 may comprise suitable logic, circuitry, interfaces
and or code that may enable storage and/or retrieval of data and or code.
The memory 208 may utilize any of a plurality of storage medium
technologies, such as volatile memory, for example random access memory
(RAM), and/or non-volatile memory, for example electrically erasable
programmable read only memory (EEPROM).

[0054] The interference cancellation module 210 may comprise suitable
logic, circuitry and/or code that are operable to suppress interference
signals, relative to a desired signal, in a received signal. The received
signal may comprise one or more desired signals and one or more
interference signals. The interference cancellation module 210 may
generate interference suppressed versions of the one or more signals by
reducing the signal level for the interference signals relative to the
signal level for the desired signals. In an exemplary embodiment of the
invention that utilizes transmit diversity, a pair of signals from a pair
of transmit antennas may be received via one or more channels by the
antenna 222 and processed by system 200. In the case of Tx diversity, the
same scrambling code may be used on multiple transmit antennas. The
interference cancellation module may treat each transmit antenna as an
independent interferer, estimate each interfering signals, and subtract
the interfering signals from the received signal that is a composition of
signals from multiple sources including the multiple transmit antennas.
This may lead to a single interference being subtracted multiple times
and therefore amplifying the detrimental effects of the interference. In
order to avoid this, the channel estimation from each antenna is
preprocessed such that the resulting channel estimation representations
have little mutual-correlation.

[0055] In operation, the receiver 202 may receive signals via the
receiving antenna 222. In an exemplary embodiment of the invention, the
receiver 202 may comprise a rake receiver. The receiver 202 may
communicate signals to the processor 206 and/or to the interference
cancellation module 210.

[0056] The receiver 202 may generate timing information that corresponds
to each of the fingers in the rake receiver portion of the receiver 202.
Each of the fingers in the rake receiver may process signals that are
received from a particular BTS within a delay spread time duration. Based
on the received RF signals, the receiver may generate chip level baseband
signals. The receiver 202 may communicate the chip-level baseband signals
to the interference cancellation module 210. The rake receiver 202 may
generate one or more symbol-level baseband signals based on a selected
one or more OVSF codes and a selected one or more PN sequences. The
symbol-level baseband signals may be communicated to the processor 206.
The OVSF codes may be selected based on a specified desired user signal.
For example, referring to FIG. 1B, the rake receiver 202 associated with
mobile communication device MU_2 may select an OVSF code, WC_12, and PN
sequences PN_A and PN_D, which may be utilized to generate the
symbol-level baseband signal from the chip-level baseband signal.

[0057] The processor 206 may utilize common pilot channel (CPICH)
information, communicated by the signals received from the receiver 202,
to compute a plurality of channel estimate values or, in various
embodiments of the invention, the receiver 202 may compute the channel
estimate values. The processor 206 and/or receiver 202 may compute one or
more channel estimate values corresponding to multipath signals
transmitted by one or more BTSs and received at a finger in the rake
receiver. The computed channel estimate values may be represented as a
channel estimate matrix, w''b,t,r,f, where `b` represents a
numerical index that is associated with a given BTS, `t` represents a
numerical index that is associated with a given transmit antenna of the
BTS `b`, `r` represents a numerical index that is associated with a given
receive antenna of the system 200, and f represents a numerical index of
the rake fingers associated with the transmit antenna `t` of the BTS `b`.
The processor 206 may be operable to communicate the computed channel
estimate values to the receiver 202 and to the interference cancellation
module 210 and/or to the memory 208. The processor 206 may compute and/or
select one or more interference cancellation parameter values, which
control the signal interference cancellation performance of the
interference cancellation module 210. The processor 206 may also be
operable to communicate the interference cancellation parameter values to
the interference cancellation module 210 and/or to the memory 208.

[0058] The processor 206 may also determine which BTSs are associated with
a current cell 100 and which BTSs are not associated with the current
cell 100. For example, the processor 206 may determine that the BTS A 102
and the BTS B 104 are associated with the current cell 100, while the BTS
C 106 is not associated with, the current cell 100. In an exemplary
embodiment of the invention, the processor 206 may store one or more PN
sequences for at least a portion of the BTSs that are associated with the
current cell 100. For example, referring to FIG. 1B, the processor 206
may generate and/or store corresponding PN sequences, for example PN_A,
PN_D, and PN_B, in the memory 208. The PN sequences may be generated on
the fly based on the code structure utilized by the BTS and/or based on
timing information associated with the BTS. The PN sequences PN_A, PN_D
and PN_B may be associated with the current cell 100.

[0059] In other exemplary embodiments of the invention, the processor 206
may store PN sequences for at least a portion of the BTSs that are
associated with the current cell 100 and at least a portion of the BTSs
that, are not associated with the current cell 100. For example,
referring to FIG. 1B, the processor 206 may generate and/or store
corresponding PN sequences, for example PN_A, PN_B PN_C, and PN_D in the
memory 208. In general, the processor 206 may store the PN sequences for
the BTSs from which a mobile communication device, for example the mobile
communication device MC_2 114, may expect to receive signals and the
processor 206 may store PN sequences from which the mobile communicating
device may not expect to receive signals. The mobile communication device
may expect to receive signals, for example common pilot channel (CPICH)
signals, from, a plurality of BTSs in anticipation of a soft handoff from
a current service BTS to a subsequent serving BTS.

[0060] The interference cancellation module 210 may receive signals from
the receiver 202, which correspond to received multipath signals. The
signals received by the interference cancellation module 210 may comprise
chip-level baseband signals. A plurality of chips, for example 256 chips,
may be associated with a data symbol. The interference cancellation
module 210 may be operable to determine a time duration that corresponds
to a data symbol processing period. The interference cancellation module
210 may be operable to determine whether to perform iterations of a
signal interference suppression on received chip-level baseband signals
and/or symbol-level baseband signals, in accordance with an embodiment of
the invention, during each data symbol processing period.

[0061] The interference cancellation module 210 may retrieve a plurality
of channel estimate values, one or more PN sequences, a plurality of OVSF
codes, and one or more interference cancellation parameter values from
memory 208. The interference cancellation module 210 may receive timing
information from the receiver 202 that corresponds to each of the fingers
in the rake receiver portion of the receiver 202.

[0062] The interference cancellation module 210 may process received
signals, utilizing received timing information and channel estimate
values, to combine the multipath signals which are associated with
corresponding fingers in the rake receiver. In various embodiments of the
invention, the interface cancellation module 210 may combine the
multipath signals to generate a combined chip-level signal by utilizing,
for example, maximal ratio combining (MRC) and/or equal gain combining
(EGC). The interference cancellation module 210 may process the combined
chip-level signal, by utilizing PN sequences and OVSF codes, to determine
a signal level associated with each of the plurality of OVSF codes for
each of one or more selected PN sequences. In an exemplary embodiment of
the invention, the plurality of OVSF codes comprises 256 Walsh codes.
Each signal associated with an OVSF code may be referred herein as a
corresponding user signal, although it should be noted that multiple OVSF
codes may be associated with a single user and thus there is not
necessarily a one-to-one correspondence between OVSF codes and users. For
example, a signal associated with a jth OVSF code may be referred to
as a jth user signal. Referring to FIG. 1, for example, the OSVF
code WC_12 may be associated with a user signal that is transmitted from
BTS A 102 to the mobile telephone MC_2 114.

[0063] The interference cancellation module 210 may compute a signal power
level value and a noise power level value corresponding to each of the
user signals. Based on the computed signal power level value, noise power
level value, and the one or more interference cancellation parameter
values, the interference cancellation module 210 may compute a weighting
factor value corresponding to each user signal. The plurality of
weighting factor values associated with each BTS may be represented as a
weighting factor matrix, Abts, where bts represents a numerical
index value that is associated with a given BTS. In an exemplary
embodiment of the invention, the weighting factor values for a given BTS
may be computed as illustrated by the following equations:

where zj represents the weighting factor value for the jth user
signal and j may be, for example, an integer from 0 to J; xj2
represents the signal power level value for the jth user signal,
which was generated by descrambling a received signal based on a PN
sequence for the given BTS and despreading the descrambled signal
utilizing the OVSF code associated with the jth user; yj2
represents the noise power level value for the jth user signal,
which was generated by descrambling the received signal based on the PN
sequence for the given BTS and despreading the descrambled signal
utilizing the OVSF code associated with the jth user; and λ
and γ represent interference cancellation parameter values.

[0064] The weighting factor values zj may correspond to a signal to
noise ratio (SNR) measure for the jth user signal. Values for
zj may be within the range 0≦zj2≦1. In one
regard, values of zj may be an a priori measure of confidence that a
given user signal comprises valid signal energy that was transmitted by
the BTS.

[0065] The interference cancellation module 210 may be operable to process
chip-level signals received from one or more transmit antennas of one or
more BTSs to generate corresponding interference suppressed chip-level
signals based on an iterative method for interference cancellation, in
accordance with an embodiment of the invention. The interference
suppressed chip-level signals may be output, to each corresponding rake
finger. Each of the rake fingers may then process its respective
interference suppressed chip-level signals.

[0066] The weighting factor value z(j) is a function of the interference
cancellation parameter values λ and γ. In various embodiments
of the invention, the interference cancellation parameters λ and
γ may comprise integer and/or non-integer values. In an exemplary
embodiment of the invention, λ=1 and γ=1. The processor 206
may be operable to monitor the interference cancellation performance of
the interference cancellation module 210, for example by measuring SNR
values for processed signals generated by the receiver 202 based on
interference suppressed chip-level signals. Accordingly, the processor
206 may be operable to adjust one or both interference cancellation
parameter values λ and γ.

[0067] FIG. 3 is a diagram of an exemplary WCDMA receiver with
interference suppression, in accordance with an embodiment of the
invention. Referring to FIG. 3, there is shown a WCDMA receiver 300 which
may be substantially similar to the receiver 200. The receiver 300 may
comprise an interference cancellation module 302, a delay buffer 304, a
HSDPA processor 306, an HSDPA switching device 308, interference
cancellation (IC) bypass switching device 310, and a plurality of rake
fingers 3121-312F. The interference cancellation module 302 may
correspond to the interference cancellation module 210 as presented in
FIG. 2. The rake fingers 3121-312F represent fingers in a rake
receiver. In an exemplary embodiment of the invention, the HSDPA
switching device 308 and the IC bypass switching device 310 may be
configured by the processor 206.

[0068] The delay buffer 304 may comprise suitable logic, circuitry,
interfaces and/or code that may be operable to receive a burst of a
chip-level signal 324 as input at a given input time instant and output
it as a burst of a chip-level signal 326 at a subsequent output time
instant. The time duration between the input time instant and the output
time instant may be referred to as a delay time duration. In an exemplary
embodiment of the invention, the delay time duration corresponds to 512
chips.

[0069] The HSDPA processor 306 may comprise suitable logic, circuitry,
interfaces and/or code that may be operable to provide HSDPA processing
of received signals.

[0070] In operation, the HSDPA switching device 308 may comprise suitable
logic, circuitry, interfaces and/or code that are operable to select an
input signal to the HSDPA processor 306. As illustrated with respect to
FIG. 3, the HSDPA switching device 308 is configured so that it is
operable to supply an interference suppressed signal 328, generated by
the interference cancellation module 302, as an input to the HSDPA
processor 306. As indicated in FIG. 3, this configuration of the HSDPA
switching device 308 may result in the HSDPA switching device 308
operating in a HSDPA interference cancellation (IC) mode.

[0071] The HSDPA switching device 308 may also be configured so that it is
operable to supply the baseband signal 324, generated by the receiver
202, as an input to the HSDPA processor 306. As indicated in FIG. 3, this
configuration of the HSDPA switching device 308 may result in the HSDPA
switching device 308 operating in a normal HSDPA mode.

[0072] Tne HSDPA switching device 308 may also be configured such that no
input signal is supplied to the HSDPA processor 306. As indicated in FIG.
3, this configuration of the HSDPA switching device 308 may result in the
HSDPA switching device 308 operating in a HSDPA data path off mode.

[0073] The IC bypass switching device 310 may comprise suitable logic,
circuitry, interfaces and/or code that are operable to select an input
signal to the rake fingers 3121-312F. As illustrated by FIG. 3,
the IC bypass switching device 310 is configured so that it is operable
to supply an interference suppressed signal 322, generated by the
interference cancellation module 302, as an input to the rake fingers
3121-312F.

[0074] The IC bypass switching device 310 may also be configured so that
it is operable to supply a signal 326, which is output from the delay
buffer 304, as an input to the rake fingers 3121-312F. The
signal 326 output from the delay buffer 304 may comprise a time-delayed,
and possibly up-sampled or down-sampled, version of the signal 324
generated by the receiver 202. As indicated in FIG. 3, the signal 326
output from the delay buffer 304 may comprise unsuppressed interference.

[0075] Each of the rake fingers 3121-312F may receive, as input,
the chip-level baseband signal 324 generated by the receiver 202. Based
on the input baseband signal 324 from the receiver 202, each of the rake
fingers 3121-312F may generate one or more channel estimates
and rake finger timing information. In various embodiments of the
invention, each rake finger 3121-312F may generate the channel
estimates and/or rake finger timing information for selected multipath
signals based on CPICH data received via the input baseband signal 324
received from the receiver 202. In the case of a single receive antenna,
each finger 312f may be allocated and/or associated with one or more
transmit antennas of a particular BTS and may generate channel estimates
w''b,t(f), for 1≦t≦T(b), where T(b) represents the
number of transmit antennas of the BTS `b`. The channel estimate
w''b,t(f) may indicate the complex channel gain between the antenna
`t` of BTS `b` and the receiver 300, for the finger `f`. In an exemplary
embodiment of the invention, the receiver 300 may comprise fingers
3121-3128, fingers 3121-3124 may be allocated for
processing signals from a first transmit-diversity BTS, and fingers
3125-3128 may be allocated for processing signals from a second
transmit-diversity BTS. In such an embodiment of the invention, the
generated channel estimates may be as depicted in Table 1.

[0076] In another exemplary embodiment of the invention, the receiver 300
may comprise eight fingers; fingers 3121-3124 may be allocated
for processing signals from transmit-diversity BTS b=1, fingers
3125-3126 may be allocated for processing signals from
non-diversity BTS b=2, and fingers 3127-3128 may be allocated
for processing signals from non-transmit-diversity BTS b=3. The channel
estimates w''b,t(f) for such an exemplary embodiment are depicted in
table 2.

[0077] In instances that the receiver comprises a plurality `R` of receive
antennas, each rake finger 312f may generate channel estimates
w''b,t,1(f) . . . w''b,t,R(f), for 1≦t≦T(b) and
1≦r≦R. The channel estimate w''b,t,r(f) may indicate
the complex channel gain between the antenna `t` of BTS `b` and the
receive antenna `r` of the receiver 300, for the finger `f`. In an
exemplary embodiment of the invention, the receiver 200 may comprise two
receive antennas and eight fingers, fingers 3121-3124 may be
allocated for processing signals from transmit-diversity BTS b=1, fingers
3125-3128 may be allocated for processing signals from
transmit-diversity BTS b=2. In such an embodiment, the channel estimates
depicted in table 3 may be generated.

[0078] Each rake finger 3121-312F may communicate, as one or
more signals 318, its respective channel estimates, rake finger timing
information, scrambling codes associated with one or more BTSs, and/or
other information to the interference cancellation module 302.

[0079] In various embodiments of the invention, the interference
cancellation module 302 may receive chip-level signals 326 from the delay
buffer 304. Based on the channel estimates, rake finger timing, and/or
other information communicated via the signal(s) 318, the interference
cancellation module 302 may select individual multipath signals from the
chip-level signals 326 received via the delay buffer 304. Based on the
interference cancellation parameters 320, which may be as described with
respect to FIG. 2, the interference cancellation module 302 may process
the received chip-level multipath signal 326 utilizing an iterative
method for interference cancellation, in accordance with an embodiment of
the invention.

[0080] The chip-level signals 326 received from the delay buffer 304 may
comprise a plurality of multipath signals received via one or more
receive antennas from one or more transmit antennas of one or more BTSs.
The interference cancellation module 302 may be configurable to assign
signal processing resources to perform the iterative method of
interference cancellation for selected multipath signals. The processor
206 may configure the interference cancellation module 302 to receive
multipath signals from one or more transmit antennas of one or more BTSs.
The processor 206 may configure the interference cancellation module 302
for receive diversity.

[0081] The interference cancellation module 302 may receive interference
cancellation parameters 320 from the processor 206 and/or from the memory
208. In an exemplary embodiment of the invention, the interference
cancellation module 302 may generate and/or retrieve PN sequences and/or
OVSF codes from the memory 208. The interference cancellation module 302
may retrieve aid/or generate a PN. sequence for each of the one or more
transmit antennas of the one or more BTSs from which the interference
cancellation module 302 is configured to attempt to receive a signal.

[0082] In various embodiments of the invention in which the receiver 202
utilizes a plurality of receiving antennas and/or receives data from a
plurality of transmit antennas, data received via the symbol-level
signals corresponding to the plurality of receiving antennas and/or
transmit antennas may be decoded by utilizing various diversity decoding
methods. Various embodiments of the invention may also be practiced when
the receiver 202 is utilized in a multiple input multiple output (MIMO)
communication system. In instances where the receiver 202 is utilized in
a MIMO communication system, data received via the symbol-level signals,
received via the plurality of receiving antennas, may be decoded by
utilizing various MIMO decoding and/or diversity decoding methods.

[0084] The CHEST pre-processing module 401 may comprise suitable
circuitry, logic, interfaces, and/or code that may be operable to
normalize and/or orthogonalize channel estimate information input as
signal 412 to the Per-Cell Modules 403 and the interpolator 411. The
normalization may be based on channel estimate and rake finger timing and
scaling information 318 received from the rake fingers
3121-312K. Additional details of the CHEST pre-processing
module 401 are described below with respect to FIGS. 5-8.

[0085] The subtractor 405 may comprise suitable circuitry, logic,
interfaces, and/or code that may be operable to subtract estimated
signals from received signals as part of the generation of an
interference suppressed version of the received signals. The subtractor
405 may be operable to receive, as inputs, signals generated by the
Per-Cell modules 403A-403D that may be interpolated by the interpolator
411, as well as 256-chip bursts of the delayed received signal 326 from
the delay buffer 304.

[0086] The HSDPA interpolation and delay module 407 may comprise suitable
circuitry, logic, interfaces, and/or code that may be operable to provide
a bypass path for signals received from the delay buffer 304. The HSDPA
interpolation and delay module 407 may, for example, interpolate cx2
samples to cx16 samples, and may introduce a delay that equals the delay
of the interference cancellation module 302 when operating in
interference cancellation mode.

[0087] The finger MUX 409 may comprise suitable circuitry, logic,
interfaces, and/or code that may be operable to select from the plurality
of signals 420 generated by the Per-Cell modules 403A-403D, the input
signal from the delay buffer 304, or a non-cancelling finger input 424.
In this manner, the finger MUX 409 may enable a pass-through mode, an
interference cancelling mode, or a non-cancelling mode.

[0088] The interpolator 411 may comprise suitable circuitry, logic,
interfaces, and/or code that may be operable to interpolate a received
signal, such as a cx1 signal and output a cx2 signal, for example.

[0089] The Per-Cell modules 403A-403D may each comprise suitable
circuitry, logic, interfaces, and/or code that may be operable to
generate an estimate of a multi-user (e.g., WCDMA) and/or multipath
chip-level signal. Each of the Per-Cell modules 403A-403D may process
bursts--256-chip bursts, for example--of a received multi-user and/or
multipath signal. A received signal 326 processed by each of the modules
403A-403D may comprise information received on one or more RF channels
via one or more receive antennas from one or more transmit antennas of
one or more BTSs, each BTS having up to J users. In this regard, each of
the modules 403A-403D may be allocated for processing signals from a
particular transmit antenna of a particular BTS, where the signals from a
particular transmit antenna may be received over one or more RF channels
via each of one or more receive antennas. Accordingly, each of the
modules 403A-403D may be operable to provide compensation for multipath
effects, suppress interference from BTSs other than an associated or
"serving" BTS, and suppress interference between users of the associated
or "serving" BTS.

[0090] In an exemplary embodiment of the invention, the four Per-Cell
modules 403A-403D may be operable to cancel and/or suppress interference
from four non-diversity transmit (Tx) BTSs, two Tx diversity BTSs, one Tx
diversity BTS and two non-Tx diversity BTSs, one Tx diversity BTS with
two scrambling, codes, per antenna, and/or one non Tx-diversity BTS that
has four scrambling codes. However, the invention need not be so limited,
and may support any number of cells depending on the number of Per-Cell
modules integrated in the interference cancellation module.

[0091] In operation, each one of the per-cell modules 403a-403d may be
allocated for processing signals from a particular transmit antenna `t`
of a particular BTS `b`. Accordingly, each one of the per-cell modules
403a-403d that processes signals from an antenna `t` of a BTS `b` may
receive a set of normalized channel estimates wb,t,1(1)
wb,t,R(F(b)) from the CHEST pre-processing module 401. In this
regard, the CHEST pre-processing module 401 may generate the set of
normalized channel estimates wb,t,1(1) . . . wb,t,R(F(b)) by
processing the set of channel estimates w''b,t,1(1) . . .
w''b,t,R(F(b)) received from the rake fingers
3121-312F(b), allocated to processing signals from the antenna
`t` of BTS `b`. Processing of the set of channel estimates
w''b,t,1(1) . . . w''b,t,R(F(b)) may comprise orthogonalization
and/or normalization.

[0092]FIG. 5 is a diagram illustrating generation of normalized channel
estimates, in accordance with an embodiment of the invention. Referring
to FIG. 5 there is shown an exemplary CHEST pre-processing module 401
comprising a switching element 502, an orthogonalization module 602, and
a normalization module 702.

[0093] The switching module 502 may comprise suitable logic, circuitry,
interfaces, and/or code that may be configurable such that channel
estimates either bypass the orthogonalization module 602 or are processed
by the orthogonalization module 602. The switching module 502 may be
controlled by one or more control signals from, for example, the
processor 206 (FIG. 2).

[0094] The orthogonalization module 602 may comprise suitable logic,
circuitry, interfaces, and/or code that may be operable to determine a
measure of correlation between a set of channel estimates from a first
antenna of a transmit-diversity BTS and a set of channel estimates from a
second antenna of the transmit-diversity BTS. Based on the measure of
correlation, the orthogonalization module 602 may set each of the channel
estimates from the second antenna to zero. That is, signals from the
second antenna may be disregarded or ignored for interference
cancellation processing. Alternatively, based on the measure of
correlation, the orthogonalization module 602 may rotate the set of
channel estimates from the second transmit antenna such that the rotated
set of channel estimates is orthogonal to the set of channel estimates
from the first transmit antenna. In this regard, the set of channel
estimates from the first transmit antenna may be represented as a first
vector having F(b) elements and the set of channel estimates from the
second transmit antenna may be represented as a second vector having F(b)
elements. Accordingly, the second vector may be rotated such that the
rotated vector is orthogonal to the first vector.

[0095] The normalization module 702 may comprise suitable logic,
circuitry, interfaces, and/or code that may be operable to normalize
channel estimates with respect to total power from a particular BTS or a
particular transmit antenna of a BTS received via one or more signal
paths. In this regard, in instances that signals are received from a
particular BTS or particular transmit antenna of a BTS via a single path,
the channel estimates may be set to one. In instances that signals from a
particular BTS or particular transmit antenna are received over a single
path, then the channel estimates may be normalized to values between 0
and 1. In instances that signals from a particular BTS or particular
transmit antenna are received over multiple paths then the channel
estimates may be normalized to values between 0 and 1.

[0096] The normalization may ensure that the estimated interference signal
to be subtracted from a received signal is appropriately scaled. If the
interference signal is too large, the subtracted interference signal may
be more than the actual interference; this may have the undesired effect
of effectively introduce interference. Conversely, if the interference
signal is too small, the subtracted interference signal only represents a
portion of the interference; this may have the undesired effect of
interference remaining in, the received signal after cancellation.

[0097] In operation, the switching module 502 may be dynamically
configured as channel estimates are received from the fingers
3121-312F. In this regard, for estimates received from a finger
312f associated with a non-transmit-diversity BTS, the switching
module 502 may route the channel estimates w''b,t,r(f) to the
normalization module 702. Conversely, for estimates received from, a
finger 312f associated with a transmit-diversity BTS, the switching
module 502 may route the channel estimates w''b,t,r(f) to the
orthogonalization module 602.

[0098] In an, exemplary embodiment of the invention, fingers
3121-312F(b) may be allocated for processing signals from a
non-transmit-diversity BTS `b`. In such an embodiment, the set of channel
estimates w''.sub.b,1,1(1) . . . w''.sub.b,1,R(F(b)) may bypass the
orthogonalization module 602 and the set of normalized channel estimates
w.sub.b,1,1(1) w.sub.b,1,R(F(b)) may be generated by normalizing the set
of channel estimates w''.sub.b,1,1(1) w''.sub.b,1,R(F(b)) with respect to
the total signal energy received via the rake fingers
3121-312F(b). The set of normalized channel estimates
w.sub.b,1,1(1) . . . w.sub.b,1,R(F(b)) may be communicated to the one of
the per cell modules 403a-403d allocated for processing signals from the
BTS `b`. The per-cell module may utilize the normalized channel estimates
for cancelling interference in signals received from the BTS `b`. Channel
estimates may be processed in this manner for each non-transmit-diversity
BTS for which there is a per-cell module 403 and one or more fingers 312
that are allocated.

[0099] In an exemplary embodiment of the invention, fingers
3121-312F(b) may be allocated for processing signals from a
transmit-diversity BTS `b`. In such an embodiment, the two sets of
channel estimates w''.sub.b,1,1(1) . . . w''.sub.b,1,R.sup.(F(b)) and
w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)) may be routed to the
orthogonalization module 602. The orthogonalization module 602 may be
operable to generate corresponding sets of channel estimates
w'.sub.b,1,1(1) . . . w'.sub.b,1,R(F(b)) and w'.sub.b,2,1(1) . . .
w'.sub.b,2,R(F(b)) which may be conveyed to the normalization module 702,
where each set of channel estimates may be processed in the same manner
as a set of channel estimates from a non-transmit-diversity BTS.

[0100] The orthogonalization module 602 may be operable to determine a
measure of correlation between the set of channel estimates
w''.sub.b,1,1(1) . . . w''.sub.b,1,R(F(b)) and the set of channel
estimates w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)). In instances that
the measure of correlation is above a threshold, the orthogonalization
module 602 may generate a set of channel estimates w'.sub.b,2,1(1) . . .
w'.sub.b,2,R(F(b)) in which all estimates are equal to zero. In this
regard, the zeroed-out set channel estimates w''.sub.b,2,1(1) . . .
w''.sub.b,2,R(F(b)) may not be utilized for interference cancellation.
Accordingly, the one of the per-cell modules 403a-403d allocated for
processing signals from antenna 2 of BTS `b` may be disabled and/or not
utilized for interference cancellation. In instances that the measure of
correlation is below a threshold, the orthogonalization module 602 may be
operable to process the two sets of channel estimates w''.sub.b,1,1(1) .
. . w''.sub.b,1,R(F(b)) and w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)) to
generate two sets of channel estimates, w'.sub.b,1,1(1) . . .
w'.sub.b,1,R(F(b)) and w'.sub.b,2,1(1) . . . w'.sub.b,2,R(F(b)) that are
orthogonal to each other.

[0101] The normalization module 702 may then normalize w'.sub.b,1,1(1) . .
. w'.sub.b,1,R(F(b)) and w'.sub.b,2,1(1) . . . w'.sub.b,2,R(F(b)) to
generate two sets of normalized channel estimates, w.sub.b,1,1(1) . . .
w.sub.b,1,R(F(b)) and w.sub.b,2,1(1) . . . w.sub.b,2,R(F(b)). The set of
normalized channel estimates w.sub.b,1,1(1) . . . w.sub.b,1,R(F(b)) may
be communicated to the one of the per cell modules 403a-403d allocated
for processing signals from antenna 1 of the BTS `b`. The set of
normalized channel estimates w.sub.b,2,1(1) . . . w.sub.b,2,R(F(b)) may
be communicated to the one of the per cell modules 403a-403d allocated
for processing signals from antenna 2 of the BTS `b`.

TABLE-US-00004
for b =1:B // loop BTSs for which there is at least one per-cell module
allocated
Delta=Cal1=Cal2=P1=P2=P3=0; // initialize variables
if block_en==true // if the rotation block is enabled
if F(b)==1
// bypass the whole rotation part for cell b
else
for t=1:T(b) // loop through the transmit antennas of the BTS b
for r=1:R // loop through all the receive antennas of the receiver
for f=1:F(b) // loop through fingers allocated to BTS b
if t==1 // for the first transmit antenna
w`.sub.b,1,r(f) = w".sub.b,1,r(f) //bypass orthogonalization for ant. 1
else
P1 = P1 + w".sub.b,1,rH(f) w".sub.b,1,r(f) // power of ant. 1 of BTS
b
P2 = P2 + w".sub.b,2,rH(f) w".sub.b,2,r(f) // power of ant. 2 of BTS
b
P3 = P3 + w".sub.b,1,rH(f) w".sub.b,2,r(f) // Inner product
end // if t==1
end // for f=1:F(b)
end // for r=1:R
end // for f=1:T(b)
if P1==0 // if there is no signal energy received from the first antenna
w`.sub.b,2,r(f) = w".sub.b,2,r(f) // bypass orthogonalization for ant. 2
else
Cal1=P1*P2*Rth; //Rth is the correlation threshold
Cal2=P3.r*P3.r+P3.i*P3.i; //power of P3
if(Cal2>Cal1) // If measure of correlation is above a threshold
w`.sub.b,2,r(f) = 0 for all b,r // zero out estimates from antenna 2
else
β = P3/P1
for r=1:R // loop over all receive antennas
for f=1:F(b) // loop through fingers allocated to the BTS b
Delta = β*w".sub.b,1,r(f);
w".sub.b,2,r(f) = w".sub.b,2,r(f);
end // for f=1:F(b)
end // for r=1:R
end //if(Cal2>Cal1)
end //if P1==0
end // F(b)=1
else // rotation block disabled
w`b,t,r(f)= w"b,t,r(f) for all t, r, f // bypass everything for
base station b
end // if block_en==true
end // for b =1:B

TABLE-US-00005
P(t) = 0 for all t; // initialize
for b=1:B // loop BTSs for which there is at least one per-cell module
allocated
if F(b)==1 // if there is only one path for BTS b
for r=1:R // loop through all the receive antennas of the receiver
w.sub.b,1,r(1) = 1
w.sub.b,2,r(1) = 0
end
else
for t=1:T(b) // loop through the transmit antennas of the BTS b
for f=1:F(b) // loop through fingers allocated to BTS b
for r=1:R // loop through all the receive antennas of the
receiver
P(t) = sqrt(Re{w`b,t,r(f)}{circumflex over ( )}2+
Im{w`b,t,r(f)}){circumflex over ( )}2+P(t){circumflex over ( )}2 )
end
end
if (P(t)==0)
wb,t,r(f) = 0, for all f,r
else
wb,t,r(f) = w`b,t,r(f) / P(t) for all f,r
end
end
end

[0104]FIG. 6A is a diagram that illustrates exemplary orthogonalization
of channel estimates received from a transmit diversity antenna, in
accordance with an embodiment of the invention. Referring, to FIG. 6A
there is shown two sets of input channel estimates w''.sub.b,1,1(1) . . .
w''.sub.b,1,R(F(b)) and w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)), and
two sets of output channel estimates w'.sub.b,1,1(1) . . .
w'.sub.b,1,R(F(b)) and w'.sub.b,2,1(1) . . . w'.sub.b,2,R(F(b)).

[0105] In operation, the input set of channel estimates corresponding to a
first transmit antenna may bypass the rotation module 604. That is, the
channel estimates w'.sub.b,1,1(1) . . . w'.sub.b,1,R(F(b)) may be the
same as the channel estimates w''.sub.b,1,1(1) . . . w''.sub.b,1,R(F(b)),
but renamed for convenience of illustration. On the other hand, the input
channel estimates corresponding to a second transmit antenna are
processed by the rotation module 604. That is, when the rotation module
is enabled, the channel estimates w'.sub.b,2,1(1) . . .
w'.sub.b,2,R(F(b)) are a modified version of the channel estimates
w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)).

[0106] In instances that the rotation module 604 is disabled, both sets of
input channel estimates may pass directly to the output channel
estimates. Conversely, in instances that the rotation module 604 is
enabled, the output of the rotation module 604 may depend on a measure of
correlation between the two sets of input channel estimates. In this
regard, in instances that the correlation between the two sets of input
channel estimates are highly correlated (i.e. a measure of correlation
between them is above a threshold), then the rotation module 604 may
output all zero values for the set w'.sub.b,2,1(1) . . .
w'.sub.b,2,R(F(b)). That is, signals from the second antenna may be
disregarded and/or not utilized for interference suppression. On the
other hand, in instances that the two sets of input channel estimates are
not highly correlated, then the set of input channel estimates
w''.sub.b,2,1(1) . . . w''.sub.b,2,R(F(b)) may be processed to generate a
set of channel estimates w'.sub.b,2,1(1) . . . w'.sub.b,2,R(F(b)) that is
orthogonal to the set w'.sub.b,1,1(1) . . . w'.sub.b,1,R(F(b)).

[0107] Although FIG. 6A depicts modifying channel estimates corresponding
to a second antenna while channel estimates from a first antenna bypass
such modification, the invention is not so limited. For example, channel
estimates corresponding to a first antenna may be modified while channel
estimates corresponding to a second antenna bypass the modification.
Similarly, channel estimates corresponding to both antennas may be
modified. In this regard, how the channel estimates are modified is not
important so long as the result is sets of channel estimates that are
orthogonal to one another.

[0108]FIG. 6B and FIG. 6c are diagrams that illustrate exemplary
implementation of an orthogonalization module, in accordance with an
embodiment of the invention. In this regard, FIGS. 6B and 6C may
illustrate pictorially what is described above in the exemplary
pseudocode for the orthogonalization module 602.

[0109] Referring to FIG. 6B, the multipliers 6201-620FB, the
adder 626, and the formatting module 632a may generate P1. Similarly, the
multipliers 6221-622FB, the adder 628, and the formatting
module 632b may generate P2. The multipliers 6241-624FB, the
adder 630, and the formatting module 632c may generate P3. The module 640
may generate Cal2 by determining the magnitude, or an approximation of
the magnitude, of P3.

[0110] The decision block 634 may determine whether P1 is equal to zero.
In instances that P1 is equal to zero, then the set of channel estimates
the set of channel estimates w''.sub.b,2,r(f) may pass through to become
w'.sub.b,2,r(f). That is, orthogonalization may be bypassed.

[0111] In instances that P1 is not equal to zero, multiplier 636 may
multiply P1 and P2, multiplier 638 may multiple the output of multiplier
636 by a correlation threshold to generate Cal1. The correlation
threshold may be programmed via, for example, firmware. The comparison
block 642 may determine whether Cal2 is greater than Cal1. In instances
that Cal 2 is greater, then w'.sub.b,2,r(f) may be set to zero for all r
and f associated with the BTS `b`. In instances that Cal2 is not greater,
then, referring now to FIG. 6c, P3 may be divided by P1 in block 652. The
output of block 652 may be multiplied by w'.sub.b,1,r(f), for all r and f
associated with the BTS `b`, via the multiplier 656. The output of
multiplier 565 may be multiplied by a formatted version of
w'.sub.b,2,r(f), for all r and F associated with BTS `b`, via the
multiplier 658. The output of the multiplier 658 may be the modified set
of channel estimates w'.sub.b,2,r(f).

[0112] Also shown in FIGS. 6B and 6c are various formatting modules 632.
The formatting module 632 may, for example, adjust a bit-width,
left-shift, right-shift, or adjust a sample rate of a signal. One or more
of the formatting modules 632 may be optional.

[0113] It should be noted that FIG. 6B is a functional block diagram that
does not necessarily depict a hardware configuration of the
orthogonalization module 602. In this regard, various operations
associated with orthogonalization may be performed sequentially by shared
hardware and/or in parallel by separate hardware modules or blocks and
the invention is not limited to any particular hardware implementation.

[0114] FIG. 7 is a diagram that illustrates an exemplary implementation of
a normalization module, in accordance with an embodiment of the
invention. In this regard, FIG. 7 may illustrate pictorially what is
described above in the exemplary pseudocode for the normalization module
702. Referring to FIG. 7, the modules 752 and 753 may generate
pseudo-amplitude values to generate P(i). The decision block 754 may
determine whether P(i) is equal to 0, for all i. In instances that P(i)
is equal to 0 for all i, then the set of channel estimates wb,t,r(f)
may be set to 0 for all r and f associated with BTS `b`. In instances
that P(i) is not equal to 0 for all i, then `a`--generated by
left-shifting w'b,t,r(f)--may be divided by P(i) in block 756. If
there is more than one finger associated with the BTS `b`, then the
output of the block 756 may be selected as the set of channel estimates
wb,t,r(f) for all t, r, and f associated with BTS `b`. In instances
that there is only one finger associated with BTS `b,` then
wb,t,r(f) may be set to 1 for all t, r, and f associated with BTS
`b`.

[0115] FIG. 8 is a flowchart illustrating exemplary steps for interference
cancellation in a communication system that utilizes transmit diversity,
in accordance with an embodiment of the invention. Referring to FIG. 8,
the exemplary steps may begin with step 802 when the rake fingers
3121-312F may be allocated among one or more BTSs. That is,
each finger may be associated with a particular BTS. In step 804,
wireless signals may be received by the receiver 300 from the one or more
BTSs. In step 806, each finger may begin generating channel estimates
that estimate the complex channel gain from the one or more transmit
antennas of the associated BTS to a particular receive antenna of the
receiver 300. In step 808, for each finger, it may be determined whether
the associated BTS utilizes transmit diversity. For fingers that are
associated with a transmit diversity BTS, the exemplary steps may advance
to step 812.

[0116] In step 812, for each finger associated with a transmit-diversity
BTS, it may be determined whether a measure of correlation between a set
of channel estimates for a first transmit antenna of the associated BTS
and a set of channel estimates for a second transmit antenna of the
associated BTS is above a threshold. In instances that the measure of
correlation is above a threshold, the exemplary steps may advance to step
814. In step 814, for each finger associated with a transmit-diversity
BTS, the second set of channel estimates generated by the finger may be
processed such that the result is orthogonal to the first set of channel
estimates generated by the finger.

[0117] In step 810, for each finger, the channel estimates corresponding
to the finger may be normalized. For channel estimates corresponding to a
finger f, the normalization may be done with respect to the total energy
received by all fingers associated with the same BTS.

[0118] In step 818, each set of normalized estimate may be conveyed to a
corresponding per-cell module. In step 820, the per-cell modules may
perform interference cancellation utilizing the normalized channel
estimates.

[0119] Returning to step 812, in instances that the measure of correlation
is above a threshold, the exemplary steps may advance to step 816 in
which the channel estimates to be output to the corresponding per cell
module may be set to zero. In this regard, a per-cell module that
receives the zeroed out channel estimates may not cancel interference. In
this manner, aspects of the invention may prevent double cancellation of
the same interference.

[0120] Returning to step 808, for channel estimates from fingers
associated with a non-transmit-diversity BTS, the exemplary steps may
advance to the step 810.

[0121] Aspects of a method and system for channel estimation for
interference suppression are provided. In an exemplary embodiment of the
invention, one or more circuits and/or processors of the CHEST
pre-processing module 401 may generate and/or receive a first set of
channel estimates w''.sub.b,1,r(1) . . . w''.sub.b,1,r(F(b)) and a second
set of channel estimates w''.sub.b,2,r(1) . . . w''.sub.b,2,r(F(b)). The
first set of channel estimates may be associated with a plurality of RF
channels between a first transmit antenna 152A of a base transceiver
station 102 and one or more receive antennas 222 of the mobile
communication device 114. The second set of channel estimates may be
associated with a plurality of RF channels between a second transmit
antenna 152D of the base transceiver station 102 and one or more receive
antennas 222 of the mobile communication device 114. The one or more
circuits and/or processors may modify the second set of channel estimates
based on a comparison of a measure of correlation between the first set
of channel estimates and the second set of channel estimates with a
threshold. The first set of channel estimates w''.sub.b,1,r(1) . . .
w''.sub.b,1,r(F(b)) and/or the modified second set of channel estimates
w'.sub.b,2,r(1) . . . w'.sub.b,2,r(F(b)) may be utilized for processing
received signals. In instances that the measure of correlation is below
the threshold, the second set of channel estimates may be modified such
that the modified second set of channel estimates w'.sub.b,2,r(1) . . .
w'.sub.b,2,r(F(b)) is orthogonal to the first set of channel estimates
w''.sub.b,1,r(1) . . . w''.sub.b,1,r(F(b)). In instances that the measure
of correlation is above the threshold, the second set of channel
estimates may be modified such that the modified second set of channel,
estimates w'.sub.b,2,r(1) . . . w'.sub.b,2,r(F(b)) is a set of zeros.

[0122] The first set of channel estimates may be normalized with respect
to total power received over all of the plurality of RF channels between
the first transmit antenna 152A and the one or more receive antennas 222.
The second set of channel estimates may be normalized with respect to
total power received over all of the plurality of RF channels between the
second transmit antenna 152D and the one or more receive antennas. The
threshold may be dynamically determined. The second set of channel
estimates may be disregarded in instances that the measure of correlation
is above a threshold. Each channel estimate in the first set of channel
estimates may indicate a complex channel gain between the first transmit
antenna 152A and one of the one or more receive antennas 222. Each
channel estimate in the second set of channel estimates may indicates a
complex channel gain between the second transmit antenna 152D and one of
the one or more receive antennas 222. The base transceiver station 102
may be a non-listened base transceiver station. Interference may be
suppressed in the received signals based on the first set of channel
estimates and/or the modified second set of channel estimates.

[0123] Another embodiment at the invention may provide a machine and/or
computer readable medium, having stored thereon, a computer program
having at least one code section executable by a machine and/or computer,
thereby causing the machine and/or computer to perform the steps as
described herein for channel estimation for interference suppression.

[0124] Accordingly, the present invention may be realized in hardware,
software, or a combination of hardware and software. The present
invention may be realized in a centralized fashion in at least one
computer system, or in a distributed fashion where different elements are
spread across several interconnected computer systems. Any kind of
computer system or other apparatus adapted for carrying out the methods
described herein is suited. A typical combination of hardware and
software may be a general-purpose computer system with a computer program
that, when being loaded and executed, controls the computer system such
that it carries out the methods described herein.

[0125] The present invention may also be embedded in a computer program
product, which comprises all the features enabling the implementation of
the methods described herein, and which when loaded in a computer system
is able to carry out these methods. Computer program in the present
context means any expression, in any language, code or notation, of a set
of instructions intended to cause a system having an information
processing capability to perform, a particular function either directly
or after either or both of the following: a) conversion to another
language, code or notation; b) reproduction in a different material form.

[0126] While the present invention has been described with reference to
certain embodiments, it will be understood by those skilled in the art
that various changes may be made and equivalents may be substituted
without departing from the scope of the present invention. In addition,
many modifications may be made to adapt a particular situation or
material to the teachings of the present invention without departing from
its scope. Therefore, it is intended that the present invention not be
limited to the particular embodiment disclosed, but that the present
invention will include all embodiments falling, within the scope of the
appended claims.